Amyloidosis is a condition characterized by the accumulation of various insoluble, fibrillar proteins in the tissues of a patient. The fibrillar proteins that comprise the accumulations or deposits are called amyloid proteins. While the particular proteins or peptides found in the deposits vary, the presence of fibrillar morphology and a large amount of β-sheet secondary structure is common to many types of amyloids. An amyloid deposit is formed by the aggregation of amyloid proteins, followed by the further combination of aggregates and/or amyloid proteins.
The presence of amyloid deposits has been shown in various diseases, each with its particular associated protein, such as Mediterranean fever, Muckle-Wells syndrome, idiopathetic myeloma, amyloid polyneuropathy, amyloid cardiomyopathy, systemic senile amyloidosis, amyloid polyneuropathy, hereditary cerebral hemorrhage with amyloidosis, Alzheimer's disease, Down syndrome, Scrapie, Creutzfeldt-Jacob disease, Kuru, Gerstrnann-Straussler-Scheinker syndrome, medullary carcinoma of the thyroid, Isolated atrial amyloid, β2-microglobulin amyloid in dialysis patients, inclusion body myositis, β2-amyloid deposits in muscle wasting disease, Sickle Cell Anemia, Parkinson's disease, and Islets of Langerhans diabetes type 2 insulinoma.
A simple, noninvasive method for detecting and quantitating amyloid deposits in a patient has been eagerly sought. Presently, detection of amyloid deposits involves histological analysis of biopsy or autopsy materials. Both methods have major drawbacks. For example, an autopsy can only be used for a postmortem diagnosis.
The direct imaging of amyloid deposits in vivo is difficult, as the deposits have many of the same physical properties (i.e., density and water content) as normal tissues. Attempts to image amyloid deposits directly using magnetic resonance imaging (MRI) and computer-assisted tomography (CAT) have been disappointing and have detected amyloid deposits only under certain favorable conditions. In addition, efforts to label amyloid deposits with antibodies, serum amyloid P protein, or other probe molecules has provided some selectivity on the periphery of tissues, but has provided for poor imaging of tissue interiors.
Thus, it would be useful to have a noninvasive technique for imaging and quantitating amyloid deposits in a patient. In addition, it would be useful to have compounds that inhibit the aggregation of amyloid proteins to form amyloid deposits.
One of the most devastating diseases associated with amyloid deposits is Alzheimer's disease. Alzheimer's disease is a degenerative brain disorder characterized clinically by progressive loss of memory, cognition, reasoning, judgement, and emotional stability that gradually leads to mental deterioration and ultimately death. Because Alzheimer's disease and related degenerative brain disorders are a major medical issue for an increasingly aging population, the need for new treatments and methods for diagnosing the disorders are needed.
Several classes of compounds have been shown to have activity against Alzheimer's disease. The only two agents currently approved for clinical treatment of Alzheimer's disease are the acetylcholinesterase inhibitors tacrine and donepezil (see U.S. Pat. No. 4,816,456). U.S. Pat. Nos. 5,716,975 and 5,523,314 relate to rhodanine derivatives useful as hypoglycemic agents and for treating Alzheimer's disease.
The present invention provides a group of aminoindanyl analogs that are inhibitors of amyloid aggregation and are thus useful for treating Alzheimer's disease. The compounds are also useful as imaging agents because of their ability to selectively bind to amyloid proteins.